The second one is absolutely trivial if you've ever read K&R (even if you're not allowed to just call strcpy()), while the fourth one is also very straightforward if you know about https://news.ycombinator.com/item?id=15266331 ; but 32 years ago, knowledge definitely did not propagate as quickly as it does today.

Additionally, I was allowed to store Color however I wanted — so if I needed some precomputation, I was allowed to bake it in there.

I believe it can be done in three operations, not including the precomputation.